Sand blowing apparatus for molds and cores



1954 H. .1. a. HERBRUGGEN 2,692,409

SAND BLOWING APPARATUS FOR MOLDS AND CORES Filed July 5, 1952 v 2 Sheets-Sheet l INVENTOR. ////Y/?/CA HQfAKW 1954 H. J. B. HERBRUGGEN 2,692,409

SAND BLOWING APPARATUS FOR MOLDS AND CORES Filed July 5, 1952 2 Sheets-Sheet 2 48 W r W 4 5 :IWJZ

I I I. L\\i\\\\ 1 Patented Oct. 26, 1954 SAND BLOWING APPARATUS FOR- MOLDS AND COR-ES Heinrich J. B. Herbruggen; Cleveland, Ohio, assignor to The Federal Supply Company, Cleveland, Ghio, a corporation of Ohio Application July 5, 1952, Serial No. 297,370

5 Claims. I1

This invention relates to a sand blowing apparatus and system and more particularly to improvements in the regulation of blowing pressure in the apparatus and system.

The usual sand blowing apparatus utilizes fluid pressure to aid in conveying and propelling sand into a receptacle such as a mould, flask or core box. In practice, the sand receptacle may be provided with vents to the atmosphere for venting the fluid pressure during delivery of sand. In spite of such venting, the pressure in the receptacle is likely to build up to an undesirable value which may damage the receptacle, particularly when using frail receptacles made of wood or the like. The build-up of pressure within the receptacle also requires that the top and bottom of the receptacle be absolutely parallel to prevent sand from escaping under pressure between the blowhead and the mating side of the receptacle.

Accordingly, it is an object of this invention to regulate and control the blowing pressure to limit the pressure in a sand receptacle to a predetermined safe value.

Briefly, in accordance with this invention, there is provided a sand blowing apparatus having a sand transfer chamber with a fluid pressure inlet and exhaust. The chamber has a blow plate with a sand discharge opening for communication with a sand receptacle, and the blow plate has a venting chamber establishing communication between the receptacle and a throttle valve in the fluid pressure supply line. The sand blowing cycle may be initiated and terminated by hand or automatically by controlling the fluid pressure inlet and exhaust to the chamber. The throttle valve in the fluid pressure supply line is normally biased open against the fluid pressure from the receptacle by a biasing load which will be overcome when a predetermined safe value of pressure is attained in the receptacle to position the throttle valve and restrict the supply line opening for a restriction of delivered fluid pressure to the chamber. The consequent restriction of flow or fluid pressure through the chamber and receptacle will allow the biasing load to reopen the throttle valve and again supply increased fluid pressure to the chamber until the predetermined safe value of pressure is again reached in the receptacle. This throttling action is continuous during the blowing cycle until such time as the receptacle is filled with sand and the cycle is terminated.

In the drawings:

Fig. 1 is a vertical view in partial section of a sand blowing apparatus and control system embodying the regulated fluid pressure supply to the transfer chamber;

Fig. 2 is an enlarged detailed view of the regulating valve with its connection between the receptacle venting chamber and the fluid pressure supply line; and

Fig. 3 is a schematic diagram of an electromatic control circuit for the apparatus of Fig. 1.

The sand blowing apparatus of Fig. 1 embodies an enclosed vertical frame having a base In and a vertically spaced crosshead II interconnected with spaced vertical columns [2 and 13 to form a rigid load-distributing supporting structure. Within the top portion of the closed frame is a sand transfer chamber M which is pivotally supported at the ends of arms [5 and I6 extending from pivotal connections at the column I2 to enable limited vertical movement of the sand transfer chamber within the frame. The frame also carries at the column [2 a sand hopper l8 external to the frame and having a discharge opening it with a pivoted gate closure 20 and a loosely supported scraper ring 2|. The supporting arms l5 and it of the sand transfer chamber are pivoted to a journal !1 rotatably mounted on the column [2 to enable the sand transfer chamber I 4 to be swung about the column into fllling position under the sand hopper I8 and then back into sand blowing position within the frame.

A sand receptacle positioning mechanism in the form of a lift piston 23 is operatively disposed in the lower portion of the closed frame so that when fluid pressure is applied to the lift piston cylinder 22 the receptacle 25 is lifted upwardly against the sand transfer chamber l 4 and then the entire assembly is positioned and clamped in sand blowing relation against the frame crosshead ll. opening 25 of the sand transfer chamber communicates through a filter 21 with an exhaust space 28 in the crosshead H and the exhaust space is controlled by a spring loaded fluid pressure operated exhaust valve 29. The crosshead l I also has a valve controlled fluid pressure inlet In this position, the filling 33 which communicates with an air jacket within the sand transfer chamber.

In the preferred embodiment shown in Fig. 1, the sand transfer chamber I4 has an inner perforated partition 30 forming a sand room and carries a removable blow plate enclosure 38 at its base with a sand discharge opening v34. An agitator is rotatably supported within the sand room from a driving gear ring 36 in the top of the transfer chamber, and a spur gear 31 for driving the agitator gear ring 36 is operatively disposed outside the sand room within the air jacket of the chamber for protection against sand and dirt. The blow plate 38 at the bottom of the transfer chamber l4 carries a vent plate 40 with opening communicating between the receptacle 25 and the atmosphere for venting. Additional vent openings which do not communicate with the atmosphere but rather communicate through a venting chamber 42 in the vent plate 40 to establish communication between the receptacle 25 and a conduit 43 leading to the piston side of a butterfly control valve 44 in the main fluid pressure supply line 45, will be hereinafter more fully described.

In the preferred embodiment shown in Fig. 1, the sand blowing cycle is initiated by positioning valves 50 and 5!, which normally isolate the fluid pressure supply from the receptacle lift mechanism and the fluid pressure inlet respectively. When these valves are opened, fluid pressure is supplied from valve 5| to conduit 55 to the cross head I l and then through branches 5'! and 59 to counteract the loading springs 53 and 52 of the inlet and exhaust valves respectively and the fluid pressure inlet 33 is opened and the exhaust 28 from the sand transfer chamber is closed.

The valve 58 is first positioned to supply fluid pressure to the lift cylinder 22 to position and clamp receptacle 25 and sand transfer chamber M in sand blowing relation against the crosshead ll within the closed frame. Then fluid pressure passes through the inlet 33 and air jacket and through the perforated partition 30 into the sand room. 3! and outwardly as a propellent with the sand through the discharge opening 34 in the blow plate 38 to fill and compact the sand within the receptacle 25. Some. of the fluid pressure from the receptacle 25 will vent through the vent plate 40 to the atmosphere and some of it will vent through the venting chamber 42 and pass through the conduit 43 to the piston side of the throttle valve 44.

As best shown in Fig. 2 of the drawings, the throttle valve 44 is mounted in the main fluid pressure supply line 45 and is in the form of a butterfly valve supported on a transverse axis which cooperates with a piston rod 48. The piston rod 48 is normally biased by a spring 49 to maintain the throttle valve 44 in the supply line 45 open and the spring loading is such that it will be overcome when the fluid pressure from the receptacle 25 acting against the piston 4| reaches a predetermined safe value. When such predetermined safe value of fluid pressure is reached in the receptacle 25, the piston 4| is positioned against the spring 43 to turn the throttle valve 44 about its axis and restrict the passage in the main fluid pressure supply line 45, thereby restricting the flow of fluid pressure to the chamber inlet 33. This results in a reduction of the unit pressure within the receptacle 25 and vent conduit 42 until the spring 49 positions the piston rod 48 in the reverse direction and again opens the throttle valve 44 in the main fluid pressure supply line 45. As the result of this action, the valve 44 throttles the main fluid pressure supply line 45 to regulate the flow of fluid pressure through the chamber inlet 33 and limit the amount of pressure in the receptacle 25 to a predetermined safe value.

In the preferred embodiment of the apparatus shown in Fig. l, the fluid pressure supply conduit 56 or the valve opening of valve 54 is restricted in size to supply a restricted flow of fluid pressure which will limit the rate of lifting travel of the lift piston 23 within the cylinder to a predetermined safe rate that will prevent damage to the receptacle 25 when engaging the vent plate 4!) of the sand transfer chamber 44. The lift piston cylinder 22 also communicates with the main supply line 45 through a valve 65 which is biased closed by a spring 4| against the fluid pressure in a branch line 62. of the conduit 5'6.

The branch conduit 62 is normally isolated from the. conduit 56 by a spring loaded valve 65 which is coupled through a branch conduit 66 to the lift piston cylinder 22. When the lift piston 23 reaches the limit of its travel consequent upon the receptacle 25 and sand transfer chamber l4 engaging the crosshead ll of the frame, the pressure. developed in the lift piston cylinder 22 and branch conduit 63 is sumcient to overcome the spring loading of the valve 65. and establish communication through the branch conduit 82 between the valve it and the conduit. 55.. The pressure thus admitted to the conduit E52 is sufficient to overcome the spring loading of the valve 50 and opens the main fluid supply line 45 to. the lift piston cylinder 22 to apply an increased clamping force to the piston 23. to clamp the receptacle 25 and transfer chamber 54 in sand blowing relation within the frame. A differential exhaust valve 623 is provided in a branch line 69 from the conduit 5.6 to the lift piston cylinder 22. The valve 68. will maintain the exhaust vent ll closed until such time as the fluid pressure is removed from the conduit 58 and the pressure within the lift cylinder 22 positionsv the valve 68 to open the exhaust vent Hi.

The positioning of the valve members 55 and E! is preferably automatically controlled by electromagnetic solenoids 8t and 8% respectively which are connected in the energizing circuit shown in Fig. 3 of the drawings. In the preferred embodiment, the operation of the sand blowing cycle is initiated by momentarily compressing a starting contact 52 which energizes a solenoid 83 to position and close the contacts 64 and energize the branch circuits containing the valve operating solenoids 8G and Bl. A suitable spring biased roll latch 85 secures and holds the contacts 84 in closed position until such time as the latch is. removed by energizing the solenoid 86 in a manner that will be hereinafter more fully described.

It will be seen that the closing of the contacts 84 energizes the solenoid 84 to open the valve 543 and supply restricted fluid pressure to the lift piston cylinder 22, as previously described. The solenoid 8i controlling the valve 5! will not be energized, however, until the contactor 8! is closed. This contac-tor is actuated by a lever arm 8.8 carried by a differential valve 9% which is normally positioned in the open position under the main fluid pressure supply until such time as the pressure developed in the lift piston cylinder 22 and conduit as is sufliciently great to counterbalance the main fluid pressure supply and position valve. 90 to close the contactor 4i. This will not take place until the receptacle 25 and sand transfer chamber i i are positioned in sand blowing relation within the frame. Then, the valve 55 is positioned to supply fluid pressure to open the chamber inlet valve and close the chamber exhaust valve 29. The circuit of solenoid 8| may also be provided with a normally open series contactor 9i) which is not closed until the receptacle 25 engages the vent plate til of the sand transfer chamber E i, thereby providing a safety switch which will prevent the admission of fluid pressure to the chamber i l until after the receptacle 25 is positioned in sand blowing relation against the vent plate til. The safety contactor 8i may be placed in any suitable position in the circuit, as for example in series with the start contactor 82, to insure safe operation.

The agitator 35 within the sand room is preferably driven by an electrical motor M which has an energizing winding 92 connected in parallel With the solenoids 8E) and 8! in the circuit of Fig. 3. The motor is not energized, however, until the normally open contacts 33, in series with the energizing winding 22, are closed. These contacts 93 are closed by a switch arm B l that is carried by a fluid pressure operated valve 95 which is coupled to the developed pressure branch conduit 63 from the lift piston cylinder 22. Thus, the contacts t3 are not closed and the agitator motor not energized until the receptacle 25 and sand transfer chamber 54 are secured in clamped sand blowing relation against the crosshead ll within the frame.

In the control circuit of Fig. 3 the sand blowing cycle is automatically terminated when the receptacle 25 is filled with sand. This is accomplished by providing normally open contacts 86 in series with the latch solenoid 86 so that when the contacts 96 are closed the solenoid 86 is energized and the latch 85 removed from the contact arm of contacts 8 to open the energizing circuit to the solenoids 8i; and Bi and the agitator motor winding 92. The contacts 96 are preferably in the form of a mercury switch which is supported on a scale arm I pivoted intermediate its ends and having fluid pressure valve chambers ml and I02 formed respectively in each end. Fluid pressure is applied to the valve chambers at each end of the scale arm Hit from orifices Hi3 and its in conduits Hi5 and its leading from the air jacket of the sand transfer chamber I4. As long as the receptacle 25 is not filled with sand, fluid pressure admitted into the transfer chamber it flows from the inlet 33 through the air jacket and through the discharge opening 3t into the receptacle 25 creating a differential of pressure through the transfer chamber i i. The scale arm ifiii is so designed that as long as a differential of pressure exists within the transfer chamber M, the mercury switch 96 remains open. As soon as the receptacle 25 is filled with sand, however, the pressure within the transfer cham-- ber M is equalized to unbalance the scale arm I00 and close the mercury switch 96 which energizes the solenoid 35 and unlatches the contacts =84 to open the energizing circuit to the solenoids 8!], 8i and the agitator motor winding 92 to terminate the blowing cycle.

Thus, the sand blowing apparatus is provided with a combined fluid pressure and electrical control system which automatically initiates and terminates the blowing cycle and which performs the positioning and blowing operations in proper sequence during the cycle. The apparatus and system also limits the positioning rate of travel of the sand receptacle and the pressure in the receptacle to predetermined safe values during the blowing cycle, thereby preventing damage to the receptacle and the apparatus and insuring against the escape of sand from between the transfer chamber and the receptacle during the blowing cycle. As a result, frail sand receptacles of wood and the like which heretofore have been necessarily made by hand may now be processed in an automatically controlled sand blowing apparatus without fear of destruction or damage.

I have shown and described what I consider to be the preferred embodiment of my invention, along with similar modified forms and suggestions and, it will be obvious to those skilled in the art, that similar changes and modifications may be made without departing from the scope of my invention as described by the appended claims.

I claim:

1. In a sand blowing apparatus having a sand transfer chamber with a sand discharge opening communicating with a sand receptacle, said receptacle being provided with fluid pressure vents, said chamber having a fluid pressure inlet and a throttling valve coacting with said inlet, means coupling said throttling valve to said receptacle vents and operative in response to predetermined variations of fluid pressure in the receptacle to regulate the flow of fluid pressure through the chamber inlet and limit the pressure within the receptacle.

2. In a sand blowing apparatus having a sand transfer chamber with a discharge opening com-- maintain the valve in the open position until a predetermined safe value of fluid pressure is attained in the receptacle.

3. In a sand blowing apparatus having a sand transfer chamber arranged to communicate with a sand receptacle, a fluid pressure inlet for the chamber, a lift mechanism for positioning and clamping the sand receptacle and transfer chamber in sand blowing relation, means coacting with said lift in sand blowing position to supply fluid pressure to the chamber inlet, a throttle valve operatively supported for coaction with the chamber inlet, means operative in response to a predetermined unit pressure in the sand receptacle to position the throttle valve and regulate the flow of fluid pressure through the chamber inlet during a sand blowing cycle.

4. In a sand blowing apparatus having a sand transfer chamber with a sand discharge communicating with a sand receptacle, an inlet for Y admitting fluid pressure to the chamber, means for supplying fluid pressure to the inlet, and a throttling valve coacting with said means and operatively coupled to the receptacle for positioning by a determined fluid pressure in the receptacle to regulate the flow of fluid pressure to the inlet.

5. In a sand blowing apparatus having a sand transfer chamber with a discharge opening communicating with a sand receptacle, said chamber having a fluid pressure inlet in spaced relation 

